Realistic non-bs comparison of lithium to lead

[john61ct]

The OTS units are designed to provide the level of currents House usage would require.

Thus don't slow you down much.

For the sort of charge amps that would be needed for viable EP levels of energy (ignoring how to store it all for now),

they would have to absorb a much higher proportion of the power the sails are capturing,

thus slowing you down a lot more.

[a64pilot]

It has to slow the Boat significantly to get that much power,that is just physics.
To begin with your numbers assume 100% efficiency, and that isn’t even close to reality. I’ll do that myself to come to a concept idea, but you are talking about an existing system, these numbers should be known, they should not have to be postulated.
If what you say is correct, then there will be hundreds of them in a couple of years, there will be knock off copies too, cause anything very successful leads to that.

What your claiming reminds me of the Eclipse jet of only a few years ago, so many “experts” were running around saying there were going to be so many of them that they would shut down the National Aerospace system, etc. etc.
Those of us that had been around Aviation for a few years understood the claims were ridiculous, but that didn’t deter all the pop up experts one little bit, I’m sure fortunes were won and lost out of that fiasco.
However it proved yet again, when something sounds too good to be true, be suspicious, and before you put down your money, its best to be from Missouri the “show me state”

Like I say, I hope you right, I want it to work, however I would caution anyone against putting any money into it that you can’t afford to write off.

[KTP]

Originally Posted by a64pilot

It has to slow the Boat significantly to get that much power,that is just physics.
To begin with your numbers assume 100% efficiency, and that isn’t even close to reality. I’ll do that myself to come to a concept idea, but you are talking about an existing system, these numbers should be known, they should not have to be postulated.
If what you say is correct, then there will be hundreds of them in a couple of years, there will be knock off copies too, cause anything very successful leads to that.

It doesn't *have* to slow the boat down that much.

Say the regen prop system was 25% efficient. The boat is on a run in 20 kt wind doing hull speed, probably surfing a bit and exceeding hull speed. The boat is pushing a volume of water on the bow which would take 15kW of power to move with a pump. The boat normally can do 90% of hull speed with 9kW going to it's electric motor, so there is an extra 6kW being generated by the wind on the sails to push the boat from 90% of hull speed to the current maybe 110% of hull speed. If you were willing to sacrifice that 20% of speed, which for a 7 kt speed would be about 1.2 kt, you could theoretically generate 25% of that 6kW with your regen system, or 1.5kWh

Just one way I could see the math working...

[CatNewBee]

You are right, and just mount it at the bow instead at the stern, it will then not slow you down, but accellerate you, according to the maths, just make it negative and you will fly above hull speed and create wind...

[john61ct]

Yes maths is useful to describe observed Reality.

Used theoretically to speculate about what may be possible, not so much.

[KTP]

Math doesn't fail reality, reality fails math.

At some point the amount of water you are pushing at the bow and friction of the hull is going to make any amount of drag from a 18 inch diameter prop performing regen negligible.

If someone is seeing 150 watts from regen on a run in strong winds, it most likely means their regen system is not 25% or 100% efficient but more like 5% efficient. It would remain to be tested if this 5% efficiency could be greatly improved by changing prop size/pitch/style without effecting normal sailing and normal electric motoring.

So probably Growl has a 5% efficient prop and the Seadrive folks are more in the 25% range.

I don't know exactly how we got on this regen tangent though. I am not really expecting much on regen myself since my prop is not optimized for much of anything. I would actually be pleasantly surprised to get 200 watts from regen and only lose 0.5 kt as this would allow me to charge up the battery during the night on a crossing and only lengthen the trip time by 8%. 2400 wh for essentially free during the night would just be an added bonus to the 2000 to 4000 wh harvested during a sunny day with 1200 to 1600 watts of panels, some partial shading accounted for.

[BigBeakie]

KTP,

The regen diversion was from Post 40 when Growley commented on it.

But you are quite correct, it is thread drift from your topic of interest.

FWIW, it's clear the principles of regen are poorly understood by some here, so it may be worthy of its own thread, if anyone is interested....


Sent from my iPad using Cruisers Sailing Forum

[a64pilot]

To give my opinion of the original question LFP or lead.
I’d say lead golf cart batteries, best bang for the buck. I’d say go to lead until you get the drive part all figured out and to your liking, and then if it meets all your expectations, go to LFP. One reason is LFP from my understanding isn’t s simple drop in thing, and dealing with it and your drive system may be a whole lot to deal with all at once, break it up and it’s easier to digest, dial in the drive first.

Lead is easy, pretty much install and forget, add water every now and again and that’s all.

[GrowleyMonster]

I agree. inexpensive golf cart batteries are the best bang for the buck and the cheapest way to get your hand in the game. There are plenty of reasons to go AGM or LiFeP04 or whatever, but if none apply to you, then for a smallish boat and modest power needs, a 48v bank of golf cart batteries is a pretty decent entry level propulsion bank. For a somewhat bigger boat if you are willing to go say 96v, the same batteries, just more of them in series. For a 25' to 35' boat you can have a decent basic bank for $700 plus tax and core charge. Take good care of them and they will last a surprisingly long time. Most two year and dead FLA batteries are either not true deep cycle, or suffer from neglect.


Not much I can say with any authority on lithium types or AGM that isn't common knowledge since I haven't owned a big bank of either one, but I can tell you that I am very happy with my $85 Sams Club GC-2 batteries after four years of use. I'm sure I would like LiFeP04s too, but I cant afford them.

[alansmith]

[but that's a little too trailer park for me [/QUOTE]


GM, that cracked me up.

[alansmith]

BigBeake, thanks for posting up. Yes, they have advanced hydro gen markedly. I guess when yachtsmen are dripping money out of their aft burner ( arse) this technology just makes sense.

No matter what....there is no better bang for the buck than petroleum by products. If you have boo koo money you can blow your wad on new technology that is cleaner but never will compete with petroleum straight up. Not in my lifetime. I have looked at it a dozen times in the last three years and it never has the safety or equivalent bang for the buck.

That Servo prop is 20K plus...and doesn’t include installation or other changes to BMS. Would I like to have it. It is probably 300 % more than one of it’s rivals. But it does seduce. Thanks for the tip BigBeake.. now I will have to eat a hot fudge ice cream to calm me down. Please don’t put these things on the forum and cause sleepless nights for the common man. Smile.

[StuM]

Originally Posted by BigBeakie

Growley,

OK, I'll give you the numbers from our boat.

So it's in the water now?

[mainesail]

I would heartily recommend that anyone looking at such issues contact Bruce Schwab of Ocean Planet energy, here in Maine. The company is named after his Ocean Planet, an Open 60 sloop that took him around the world as the first American to complete the Vendee Globe race-2006 I believe. I've sailed with him a few times and besides being an expert sailor he's into technology in a big way. His boat was hyper wired up and he served as as a trial horse with several companies assisting in developing new electronica. Plus, he's a nice guy and trustworthy.
Cheers, Will

[martinwinlow]

Very much in the DIY camp, I know, but don't forget the potential for using ex-EV batteries for this application. Aside from the cost their principal advantages over lead-acid is that they can be put in a sealed box (not forgeting some form of thermal management if you system requires it) - ideal for a marine environment.
680lb would allow a 13P6S (for a 48V) system using ex-Nissan LEAF modules (from HAC V4.0) and would cost about $8k (+ BMMS). They would give a solid 30kWh of storage.

[mbullock]

For an electric boat i think you would be mad not to choose Lifepo4. Charge time... Charge rate and charge efficiency.

I blogged my reasons for lifepo4 here http://sailingdestinationanywhere.com/the-case-for-lithium-batteries/


Fair winds